1. Field of the Invention
The present invention relates to immobilizers for propeller shafts and the like. Even more particularly, the present invention relates to a propeller shaft immobilizer apparatus which hydraulically or manually immobilizes the propeller shaft when the engine propelling the shaft becomes inoperative.
2. General Background
In the use of large boats, particularly in crew boats, in servicing the offshore oil and gas industry, most of the types of craft utilized are multi-engined, in order to effectively propel the craft through the often turbulent offshore waters. It may often occur while such a craft is out to sea, that one or more of the engines in the craft may fail, and the engine, therefore, becomes inoperative. However, the propeller beneath the craft, which is operated by the engine, remains exposed to the flow of current since the craft continues to be propelled by the remaining engines. The screw-typed propeller, because of its vaned construction, continues to turn, and rotating the shaft connected thereto.
In most engine constructions of this type of craft, at the failure of the engine, a clutch mechanism re-engages the propeller shaft shince the engine is inoperative. It is only when the engine is in the operative mode that the clutch mechanism would not be in contact with the shaft, and the shaft would be allowed to rotate freely in conjunction with the operation of the engine. However, in the case of an inoperative engine, with the clutch mechanism in frictional contact with the propeller shaft, the propeller shaft will rotate freely, due to the force of the current of water through the vaned propeller, and in doing so, may cause damage to the clutch mechanism. Over a long period of time, in such cases where the crew boat is on an extended trip through the offshore waters, the damage to the clutch mechanism can be such that the clutch mechanism has to be replaced at a tremendous cost, the replacement being due solely to the fact that the rotation of the shaft against the clutch mechanism resulted in the irreparable damage to the mechanism which should be replaced.
In the present state of the art, often times crews on the crew boat, may attempt to alleviate the rotation of the shaft by several haphazard approaches. One approach would simply be to engage a linked chain around the shaft and secure the ends of the chain to the sides of the boat, so that should the shaft attempt to rotate freely in the water, the engagement of the links against the shaft may serve to prevent its rotation. However, it has been shown that this type of stopgap measure is for the most part ineffective, and when the shaft does rotate, the links of the chain in contact with the shaft simply serve to do severe damage to the shaft, and the result is the replacement not only of the clutch mechanism but of the shaft itself.
Another stopgap measure would simply be to secure a very large pipe wrench to the shaft, so that the rotation of the shaft in a certain direction would cause the pipe wrench to engage the shaft, and the handle of the pipe wrench would be so situated that the pipe wrench could not rotate, and rotation of the shaft would be prevented. However, should the shaft rotate in the opposite direction, even so slightly, the pipe wrench would, because of its construction, be dislodged from the shaft and then the shaft would be allowed to be rotating freely as with no stop measure at all.
Several patents have been secured which address the problem of a freely rotating shaft or the like, the most pertinent being as follows:
U.S. Pat. No. 3,831,547 issued to Bird entitled "Propeller Shaft Lock" would teach the use of a shaft lock for preventing rotation of a boat propeller in controlling its position when the engine is off. It has a cam mounted on the propeller shaft and a stop member which is movable into and away from the path of rotation of the shoulder member.
U.S. Pat. No. 3,786,775 issued to Sarns entitled "Shaft Lock" teaches the use of a shaft lock for auxiliary sailboats with a split flanged-collar clampable to a rotable shaft having a pair of opposed recesses. There is provided a pivotally mounted latch member adjacent a flanged collar for cooperating with the recesses in holding the shaft in certain positions. There is further provided a lever member connected to the latch member for selectively moving the latch in cooperative engagement with the recess.
U.S. Pat. No. 697,053 issued to G. Whittlesey entitled "Brake for Propeller Shafts" would teach the use of a system of mechanisms whereby the action of the engine and the propeller may be controlled and made more uniform under the varying conditions of the sea in order to avoid the many of the dangers arising from the inadequate control of the engine and moving parts.
U.S. Pat. No. 605,545 issued to Guerrant entitled "Friction Lessening Device and Brake for Propeller Shafts" would teach of a device for lessening the end thrust friction and the bearings of a screw propeller shaft of steam vessels and a brake operating upon the propeller shaft applied by reason of the increased momentum of the shaft occasioned by the propeller screw being thrown from the water upon the rising of the stern of the vessel in turbulent water.
U.S. Pat. No. 474,169 issued to A. Hellinger entitled "Regulating Propellers of Vessels" relates to means and devices for regulating the speed of revolution of the screw shaft to propellers under the varying conditions under which the boat may have to work due to rough seas or the like. Basically, it would regulate the amount of motor fluids applied to the screw engine and applying a brake to the screw shaft, both of which are operated by means of the devices for regulating the propeller momentum.
U.S. Pat. No. 278,182 issued to G. H. Reynolds entitled "Auxiliary Steam Power for Sailing Vessels" relates to the enabling of auxiliary propulsion to be applied without in the least interfering with the working of the fore and aft of the sails of the boat. The device would act on the propeller shaft for locking the propeller in such position that its blades would be maintained in a position behind the stern post when it is desirable to proceed under sail alone.